1. Field of the Invention
The present invention generally relates to silicon germanium (SiGe) technology, and more particularly to a silicon germanium carbon heterojunction bipolar transistor (SiGeC HBT) for use in various electronic devices.
2. Description of the Related Art
Silicon Germanium (SiGe) technology has become mainstream in today""s RF (radio frequency) applications, high speed wired data transmission, test equipment, and wireless applications. Silicon germanium technology provides particular benefit to heterojunction bipolar transistors (HBTs). These transistors are commonly used in semiconductor devices for high-speed operation and large drive current applications. Such heterojunction bipolar transistors are increasingly being used for applications in extremely high frequency range technologies such as communications and satellite circuitry.
A fundamental requirement of device integration in silicon is the electrical isolation of devices. Typically, resistances and capacitances associated with possible isolation schemes scale with technology. This means that as device geometries decrease, so do the isolation valves (e.g. resistance to electrostatic discharge (ESD)) of the isolation structures.
Accordingly, a need has developed in the art for HBT isolation structures that retain good resistance to ESD events.
Accordingly, it is an object of the present invention to provide improved isolatin for heterojunction bipolar transistor device.
In order to attain the object(s) suggested above, there is provided, according to one aspect of the invention, a bipolar transistor on a semiconductor substrate having a surface, comprising a shallow trench isolation (STI) in the surface, the STI having an edge; a crevice region in the STI adjacent the STI edge; a base region above the STI; a silicide above the base region; an emitter structure on the surface adjacent the base region; and a crevice cover between the emitter structure and the silicide. The crevice cover prevents substantial variation in resistance of the bipolar transistor, by preventing the silicide from extending over the crevice region. The base is spaced toward the emitter structure from the crevice region. The silicide has a resistance independent of variations in the base and the emitter structure.
The invention not only increases the spacing between the silicide and the base-to-emitter region, but also improves the silicide formation to move the silicide out of the crevice region to further improve ESD robustness. Further, the silicide has a resistance that is independent of variations in the structure of the base or the emitter structure.
The invention forms a bipolar transistor which forms a shallow trench isolation (STI) in a substrate. The STI having an edge, such that a crevice region is formed in the STI adjacent the STI edge, simultaneously growing a base region above the STI and a semiconductor of an emitter structure on the substrate adjacent the STI, forming conductors of the emitter structure above the semiconductor, forming a crevice cover on the base region adjacent the emitter structure and saliciding an upper layer of the base region and adjacent the crevice cover to produce a silicide, that includes the crevice cover maintains spacing between the emitter structure and the silicide.